TODO : use XmlReader class wherever an XML stream has to be changed into a String/Reader

TODO: integrate it to Modello

Integration Level 2: detect XML encoding for internal XML files

These files shouldn't really need special characters, since they are technical descriptors (plexus.xml and so on). But this change is useful for non-ascii platforms (Z/OS with EBCDIC), where even simple ascii characters can't be read with platform encoding.